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Fins allow the sharks to be able to guide and lift themselves. Most sharks have eight fins: a pair of pectoral fins, a pair of pelvic fins, two dorsal fins, an anal fin, and a caudal fin. Pectoral fins are stiff, which enables downward movement, lift, and guidance. The members of the order Hexanchiformes have only a single
Dorsal fin of a shark. A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom.Many species of animals possessing dorsal fins are not particularly closely related to each other, though through convergent evolution they have independently evolved external superficial fish-like body plans adapted to their marine environments ...
The first dorsal fin originates behind the short and rounded pectoral fins; the second dorsal fin is twice the size of the first and originates behind the pelvic fins. The anal fin is absent. The tail is slender, leading to a long caudal fin with a small lower lobe and a low upper lobe with a prominent ventral notch near the tip. [7]
The dorsal fins also give the shark advantages. The first dorsal fin helps the spiny dogfish maintain a stable body position while swimming while the second aids in generating thrust. [18] The caudal fin is larger than normal, which helps the sharks maneuver through the water quickly and efficiently. [19]
The first dorsal fin is large, high, stiff and angular or somewhat rounded. The second dorsal and anal fins are minute. The caudal peduncle has a few or less distinct keels. The teeth are gigantic. The fifth gill opening is in front of the pectoral fin and spiracles are sometimes absent.
According to biologists, the dorsal fin’s size in such shallow water should reveal part of the shark’s back or a second dorsal fin — neither of which are visible.
The dorsal fins are small, with the first dorsal fin origin lying behind the pelvic fin origins. There is no anal fin. The caudal peduncle is robust and lacks notches at the caudal fin origins. The asymmetrical caudal fin has an indistinct lower lobe and an upper lobe without a notch in the trailing margin. [9]
Nearly every fin of a shark is targeted for harvest, as highlighted in the diagram. The primary and secondary dorsal fins are removed from the top of the shark, plus its pectoral fins, and, in a single cutting motion, the pelvic fin, anal fin, and bottom portion of its caudal fin, or tail.